1. Field of the Invention
The present invention relates to an apparatus and method for transmitting data using a multi-antenna; and, more particularly, to an apparatus and method for transmitting data using a multi-antenna, which decides an antenna group having a proper wireless channel for data characteristics and transmit data through the decided antenna group in order to support Quality of Service (QoS).
This work was supported by the IT R&D program of MIC/IITA [2006-S-002-02, “IMT-Advanced Radio Transmission Technology with Low Mobility”].
2. Description of Related Art
It is one of objects of a next generation wireless communication system to provide various data services as well as voice service. In order to provide the various data services, it is necessary to develop a high speed data communication technology that supports a data transmit rate of several Giga-bits per second (Gbps) and Quality of Service (Qos).
A Multiple Input Multiple Output (MIMO) system uses a plurality of transmitting and receiving antennas for transmitting and receiving data. The MIMO system may incredibly increase channel capacity compared to a system using one transmitting antenna and one receiving antenna.
In order to realize such theoretical channel capacity gain of the MIMO system, various methods were introduced, such as Spatial Multiplexing and Space-Time codes.
The Spatial Multiplexing is a technology for simultaneously transmitting a plurality of data through different transmitting antennas. Therefore, the Spatial Multiplexing increases system capacity without system bandwidth increased additionally. Vertical-Bell Laboratory Layered Space-Time is one of the representative schemes thereof.
The Time-Space Code is a technology for obtaining diversity and coding gain at the same time by assigning proper codes to a data stream and transmitting data at a plurality of time slots through a plurality of antennas. Space-Time block code is one of representative schemes thereof.
For example, in a 2×2 MIMO system, a receiver receives a signal transmitted through one or more antennas from a transmitter by properly dividing the received signal. Therefore, the receiver can receive two data streams at one time slot. Also, a data error rate can be reduced by transmitting two data streams through two antennas.
That is, the MIMO system having multiple transmitting and receiving antennas can transmit at least one of data streams at the same time because of increment of transmission paths. Also, a receiving error is not generated from all of transmission paths or one predetermined wireless path.
As a method for controlling multiple transmitting antennas in the MIMO system, a physical layer applies the same data transmission scheme to multiple transmitting antennas, or applies different modulation schemes, i.e., MCS level, to each antenna in order to improve a data transmit rate of a system independently from a MAC layer. However, there is limitation to provide Quality of Service (QoS).